As one of semiconductor manufacturing processes, for example, annealing may be performed to heat a substrate present in a process chamber using a heating mechanism such as a heater so as to remove impurities from a thin film formed on a surface of the substrate. Recently, more miniaturization of semiconductor devices results in a shallow junction, and thus a lower thermal budget (thermal history) is required. However, when a substrate is heated using the heating mechanism, the whole substrate is heated to a high temperature and it may thus be difficult to decrease the thermal budget. A technique of heating a substrate present in a process chamber by radiating electromagnetic waves such microwaves to the substrate has been introduced.
A thermal budget may be lowered by heating a substrate by radiating electromagnetic waves to the substrate. However, when the substrate is heated using the electromagnetic waves, heating by the electromagnetic waves may not be uniform within a plane of the substrate. That is, the electromagnetic waves are radiated to the substrate in the process chamber, for example, via a waveguide opening formed in an upper wall of the process chamber. In general, the area of the waveguide opening is less than that of a processed surface of the substrate. The electromagnetic waves do not spread (diffuse) to a great extent after they are radiated via the waveguide opening. Thus, as the substrate is distant from a region opposite the waveguide opening, the amount of radiated electromagnetic waves may decrease. As a result, the electromagnetic waves cannot be radiated to the substrate to be uniformly distributed within a plane of the substrate, thereby preventing uniform heating within the plane of the substrate.